1. Field of the Invention
The invention relates to LED solid-state light sources and particularly to LEDs. More particularly the invention is concerned with an LED having an optically transmissive heat sink.
2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Light emitting diodes (LEDs) generate light when a current is applied to the device. However, not all of the power input into the device is converted to light. There is a large portion of energy that is given off as heat. As the semiconductor material heats up, like most electronics devices, the LED performance is degraded. This can cause decreased light output (flux), a color shift, and a reduction in device lifetime. Consequently, there is a need to efficiently remove heat from the LED chip during operation without significantly reducing light output from the package.
In most conventional electronics packages, those not emitting light, the active semiconductor chip is placed between two electrically conducting plates made of a material with a high thermal conductivity, such as copper. These plates serve as heat spreaders and effectively remove the heat from both the top and bottom surfaces of the chip. The thermal energy generated by the semiconductor chip is further dissipated by heat sinks attached to the electric plates and transported away from the chip and out of the system. Unlike semiconductor chips for power electronics, LEDs generate light, which must be extracted from the package. The opaque materials such as copper or other metal heat sinks block the light-emitting surface of the LED. Consequently, LED packages are typically only able to extract heat from one side of the chip, thereby eliminating half of the effective surface area for heat dissipation.
The present invention uses thermally conductive light transmissive materials to allow for heat dissipation on all sides of the LED without blocking the emitted light. The benefits of a heat conductive lens include: (1) a reduction in the operating temperature of LEDs, yielding increased efficiency of the LED, stable colors with little wavelength shift, and longer life; (2) increased thermal dissipation enabling the LEDs to be driven at higher currents and higher input power, yielding more light flux without overheating the LED die; and (3) the potential for adding many more heat producing devices in close proximity to the LED die, including other LED dies and integrated electronics such as resistors, capacitors, and transformers.
The use of a heat conductive lens applies to light emitting diodes (LED), ultra-violet (UV) emitting LEDs, and infrared (IR) emitting LEDs. The invention may also be used for laser diodes and any other light producing device that requires stable temperatures for operation.